switch bootloader to grub

configuration.nix

@@ -7,8 +7,12 @@
     ];
 
   # Use the systemd-boot EFI boot loader.
-  boot.loader.systemd-boot.enable = true;
-  boot.loader.efi.canTouchEfiVariables = true;
+  boot.loader.grub = {
+    enable = true;
+    version = 2;
+    device = "/dev/vda";
+  };
+  networking.hostName = "nixbox"; # Define your hostname.
 
   networking.hostName = "multiuser-server-example";